In the past three decades, electricity has risen from 25% to 40% of end-use energy consumption in the United States. With this rising demand for power comes an increasingly critical requirement for highly reliable, high quality power. As power demands continue to grow, older urban electric power systems in particular are being pushed to the limit of performance, requiring new solutions.
Metal conductors, such as copper and aluminum, form a foundation of the world's electric power system, including generators, transmission and distribution systems, transformers, and motors. The discovery of high-temperature superconducting (HTS) compounds has led to an effort to develop conductors incorporating these compounds for the power industry to replace metal conductors. HTS conductors are one of the most fundamental advances in electric power system technology in more than a century.
HTS conductors carry over one hundred times more current than do conventional metal conductors of the same physical dimension. The superior power density of HTS conductors will enable a new generation of power industry technologies. HTS conductors offer major size, weight, efficiency, and environmental benefits.
HTS technologies will drive down costs and increase the capacity and reliability of electric power systems in a variety of ways. For example, an electrical cable consisting of HTS conductors is capable of transmitting two to five times more power through existing rights of way, thus improving the performance of power grids while reducing their environmental footprint.
One way to characterize HTS conductors is by their cost per meter. An alternative way to characterize HTS conductors is by cost per kiloamp-meter. For example, by increasing the current carrying capacity for a given cost per meter of HTS conductor, the cost per kiloamp-meter is reduced. The maximum current carrying capacity is called the critical current.
Among the several issues that need to be resolved for HTS conductors to be used effectively in power transmission is AC losses. The typical approaches to reducing the AC losses in a cable incorporating HTS conductors has relied on creating nearly monolithic annuli of HTS conductors. For example, the surface of a structure supporting the HTS conductors to create the annuli is nearly completely covered with HTS conductors. However, as the HTS conductors improve in current carrying capacity, there is often more conductor used to cover the surface than is necessary to carry the current. However, often in these types of designs, reducing the amount of HTS conductors only increases AC losses.
Thus, there remains a need for a new and improved cable winding configuration that is capable of use in a system for transmitting current by taking advantage of improvements being made in superconductor conductors, while at the same time including acceptable and even improved properties with regard to AC losses.